In the words of a California state forestry official, "the winds have died down and the temperature has fallen." CBS News correspondent Stephan Kaufman (audio) reports that equation means that thousands of firefighters doing battle against the Esperanza fire are making some real progress.

The blaze, which authorities believe was deliberately set, still threatened wilderness plagued by drought and filled with dead trees.

But fire officials said the Santa Ana conditions that whipped the inferno across 63 square miles in four days had all but disappeared. They believed they could get the blaze fully contained by Monday evening.

The 2,055 firefighters battling the blaze brought containment to 90 percent. Since it started Thursday, the fire has burned 40,200 acres northwest of Palm Springs.

The price tag so far is $8.3 million, reports Kaufman.

Authorities planned to reopen highway 243 and allow hundreds of people evacuated from the Twin Pines and Poppet Flat areas to return to their homes. Many were let back into the areas briefly on Sunday to collect belongings, retrieve necessary medicine and check on animals.

"There's nothing left, just a couple of walls and rubble," said Oscar Pineiro, 52, who returned to Twin Pines with his wife to find their home in ruins.

Capt. Don Camp, a California Department of Forestry spokesman, said it was unclear when some burned-out neighborhoods would be inhabitable.

"Our goal is to get people back in their homes as quickly as possible, but until we're sure that it's safe, people are unfortunately going to be displaced," he said.

Fire officials were still concerned with the southeastern flank of the blaze, which borders a wilderness area that hasn't burned in more than 30 years and has been devastated by a bark beetle infestation that has killed hundreds of trees.

Fire analyst Timothy Chavez said fuel from the dead bark could allow the fire to creep back over the containment line.

Last week, a shift in the winds turned deadly, pushing a wall of flames around five firefighters who were trying to protect a house. Four of the firefighters died, while another was hospitalized with serious burns over most of his body.

About 50 of Cerda's relatives gathered at the hospital and prayed for him.

"They want everyone to know that Pablo's dream was to help people, and on Thursday morning, that's just what he was doing — protecting and serving," said Eddie Cortez, a family spokesman.

Vigils were held at several Southern California churches and fire stations for Cerda and to pray for the families of the fallen firefighters. Killed were Mark Loutzenhiser, 43, of Idyllwild; Jason McKay, 27, of Phelan; Jess McLean, 27, of Beaumont; and Daniel Hoover-Najera, 20, of San Jacinto.

More than 225 tips have been received by the Riverside County sheriff's office regarding the arson investigation, said Sheriff Bob Doyle.

Cabazon residents said they saw two young men leaving the fire's ignition point.

"We're keeping a real tight lid on the investigation," said Michael Jarvis, a California Department of Forestry spokesman. "We're just asking people to call in with their tips."

Another blaze broke out Sunday in Warner Springs and blackened about 100 acres. That fire forced the evacuation of about 100 homes in the rural community about 70 miles northeast of San Diego.

More than 200 firefighters, five helicopters and an air tanker rushed to the scene to defend about 14 homes in the path of the fire, which was moving east toward the Los Coyotes Indian reservation.

It was 5 percent contained Sunday evening, which was the latest information available.